I don't see it as so many kids here having sleep problems, but more showing the broad range of what is sleep in the age group

Have you looked at diet? Honestly, some foods and additives can keep kids ups. DD1 was terrible for it, thankfully DD2 not so much so. For some kids it can be something as simple as tomato dish two nights in a row. For my girls, it was a food colouring common in yoghurts, icecream etc

Another thing, is you could be trying too much, different techniques can take some time to settle in. Also some main stream technique just do not work for every kid. With us, DD1 needed music (could be techno some night), even lights, whilst DD2 needed it much darker and quieter (if anything too quiet and dark would have DD1 going hysterical).